Determination of the ultimate consolidation settlement of jack-up spudcan footings embedded in clays

Abstract

When jack-up platforms are deployed for long-term services such as those functioning as production units, the consolidation settlement of spudcan footings is an issue of particular concern. Unpredicted and thus unprepared settlement may do harm to the serviceability and safety of jack-up rigs. Through centrifuge experiment and large deformation finite element calculation, this paper first illustrates the inherent correlation between the excess pore pressure dissipation inside soil and spudcan settlement development. With the measured and calculated settlement time histories, subsequent efforts are directed towards exploring how to predict the ultimate consolidation settlement with accuracy. Particular attentions are placed on investigating the applicability and advantages of two observational methods: Asaoka's method and Hyperbolic approach. Their prediction performances for spudcan with various soil, loading, embedment and geometrical conditions are symmetrically evaluated through numerical parametric investigation. The upper and lower limits of their prediction errors are established. Explicit recommendations are given on the selection of appropriate prediction approaches for different consolidation conditions. The practical significance of these research outcomes lies in 1) providing guidance on the selection of settlement prediction approaches; 2) establishing the limits of prediction errors involved. These are expected to be particularly useful for the field monitoring of spudcan settlement.